Abstract
We numerically investigate the properties of a hybrid grating structure acting as a resonator with ultrahigh quality factor. This reveals that the physical mechanism responsible for the resonance is quite different from the conventional guided mode resonance (GMR). The hybrid grating consists of a subwavelength grating layer and an un-patterned high-refractive-index cap layer, being surrounded by low index materials. Since the cap layer may include a gain region, an ultracompact laser can be realized based on the hybrid grating resonator, featuring many advantages over high-contrast-grating resonator lasers. The effect of fabrication errors and finite size of the structure is investigated to understand the feasibility of fabricating the proposed resonator.
Highlights
A high contrast grating (HCG) structure is a near-subwavelength grating made of a highrefractive-index material and surrounded by low-refractive-index materials [1]
We numerically investigate the properties of a hybrid grating structure acting as a resonator with ultrahigh quality factor
We have shown that a hybrid grating (HG) structure can work as an ultrahigh Q-factor resonator and analysed the origin of the high-Q resonances
Summary
A high contrast grating (HCG) structure is a near-subwavelength grating made of a highrefractive-index material and surrounded by low-refractive-index materials [1]. Extensive theoretical studies of HCGs have revealed that the high index-contrast between the grating and surrounding materials is essential for achieving the extraordinary properties [12]. We have found that the combination of a near-subwavelength grating and a cap layer, both made of high-refractive-index materials and surrounded by low-refractive-index materials, as shown, can achieve a high reflectivity over a broader wavelength range than the HCG [13]. The heat generated inside the gain material can be spread out laterally in the InP cap layer as well as vertically into the Si grating layer while in the HCG resonator laser structure heat can be dissipated only laterally along the grating bars since the structure is surrounded by air. The HG resonator laser structure appears promising in many applications where compact high-speed laser is required
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